Prospective prophylaxis trial with 255 healthcare workers taking vitamin D and 2,827 controls, showing significantly lower influenza-like illness with treatment, and lower COVID-19 cases, without statistical significance. While the intervention and control groups were initially randomized, exclusions were only processed in the treatment arm.
risk of case, 97.5% lower, RR 0.02, p = 0.07, treatment 0 of 255 (0.0%), control 36 of 2,827 (1.3%), NNT 79, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm).
Effect extraction follows pre-specified rules prioritizing more serious outcomes. Submit updates
van Helmond et al., 17 Sep 2022, prospective, USA, preprint, 14 authors, study period 27 October, 2020 - 31 January, 2021, dosage 5,000IU daily, trial NCT04596657 (history)